Components Of Airflow Research Articles

Micro-environment strategy for efficient cooling in telecommunication base stations

The cooling systems of telecommunication base stations (TBSs) primarily rely on room-level air conditioners. However, these systems often lead to problems such as messy airflow, hot spots, and excessive energy consumption. With the rapid development of 5G technology, the integration and power density of communication equipment continue to increase, exacerbating these problems. To address these issues, a micro-environment strategy has been developed. This strategy combines cabinet-level airflow components with unique multi-adjustable-vent air conditioners(MAVACs), which are suitable for the co-deployment of various high power density communication equipment with different airflow patterns in TBSs. An experimental study was conducted to evaluate the cooling performance of the proposed MAVAC, and CFD simulation was carried out to investigate the temperature distribution and airflow patterns using a typical TBS in China that has implemented the micro-environment strategy. The results demonstrate that the micro-environment strategy effectively separates the cold air and hot air, preventing the occurrence of hot spots. The maximum return air temperature of MAVACs was found to be 38.6℃. Additionally, the energy efficiency ratio of the MAVAC system increases by approximately 20 % when the return air temperature is raised from 35℃ to 40℃. This study is expected to contribute to energy savings in TBSs and the successful construction of 5G networks.

In-situ empirical validation of common indoor climate parameters in an inhabited multizone dwelling

Combined building indoor climate and energy simulation models only recently gained vast popularity and their application has been moving from the research community to a broader audience. Yet, in-situ empirical validation of this new generation of complex multi-purpose dynamic simulation models has lagged behind. Using a dynamic multizone building indoor climate and energy simulation model in Modelica with the IDEAS library and buoyancy driven airflow components (validated with CONTAM), this research presents model validation results and lessons learned from an in-situ empirical validation study of common indoor climate parameters (i.e., indoor air temperature (), relative humidity (RH) and CO2 concentration (CO2)) for an inhabited and mechanically ventilated case study dwelling in The Netherlands. The simulation results show that the latest generation of building indoor climate and energy models in Modelica have great ability to accurately predict common indoor climate parameters in multizone inhabited dwellings (provided that user behavior info is available). Evaluation metrics for the three studied parameters show excellent calibration criteria (i.e., MAE between 0.60–0.78 °C (), 3.5–4.6% (RH) and 88–181 ppm (CO2)) and the accompanying graphs corroborate the findings. In the event that no motion sensor data is available, statistically generated occupancy profiles prove good representative alternatives on the condition that basic info is available about the number of inhabitants and the inhabitants’ lifestyle. In-situ monitoring for empirical model validation proves to be a real challenge full of (un)foreseen obstacles.

Influence of the downwash airflow distribution characteristics of a plant protection UAV on spray deposit distribution

During the aerial spraying of pesticides by plant protection UAVs (unmanned aerial vehicles), droplets are deposited below the aircraft under the influence of rotor airflow. The existence of a downwash airflow can improve the deposition of spray on target crops. However, during operation, variations in flight altitude and the gradual decrease in the payload of pesticide solution in the tank leads to changes in the flow field below the UAV which affects droplets distribution. In order to study this, the downwash airflow speed and droplet distributions below a UAV under different flight altitudes (1.5–3 m) and payloads (0-10 kg) were measured and analysed. The results indicated that the changes in operational parameters normally found during operation can change distribution of downwash airflow in all directions but particularly vertical and this can affect the distribution of spray below the UAV. Through correlation analysis, it was shown that the vertical component of airflow (downwash) had a significant positive correlation with spray deposition and penetration (P < 0.05, B = 0.082, B = 0.029), and a negative correlation with droplet deposition uniformity (coefficient of variation) and drift (P < 0.05, B = −3.818, B = −0.042). Thus, it can be seen that downwash is conducive to spray deposition and penetration, which can improve the droplet distribution uniformity and reduce drift. Thus, the influence mechanism of UAV airflow on droplet distribution was explored and shown to strongly influence have the quality of spraying by plant protection UAVs.

Research on Regularities of Cyclic Air Motion through a Respirator Filter

In this paper, a solution to the problem of the change in the pressure drop in a respirator filter during cyclic air motion is suggested since the current theory of filtering is based on steady-flow processes. The theoretical dependence of the pressure drop in the respirator filter on air flow rate is determined, which is represented by the harmonic law, which characterizes the human respiration process during physical work. For the calculation, a filter model was used, which is represented by a system of parallel isolated cylinders with a length equal to the total length of the filter fibres surrounded by porous shells formed by a viscous air flow field, with a size determined by the equal velocities of the radial component of air flow and undisturbed flows. The flow-around process in the proposed model of air flow through the respirator filter is described by the Brinkman equation, which served to establish the total air flow resistance in the proposed system under conditions of velocity proportionality. It consists of two parts: the first characterizes the frictional resistance of the air flow against the surface of the cylinder, which imitates the filter fibre; the second—the inertial part—characterizes the frequency of pulsations of respiratory movements during physical performance. The divergence of the analytical results and experimental studies is no more than 20%, which allows the use of the established dependence to estimate the change in pressure drop in a respirator filter made of filter material “Elephlen” when the user carries out different physical activities. This allows the period of effective protective action of respirators with different cycles of respiration during physical activities to be specified, which is a very serious problem that is not currently regulated in health and safety regulations, and it also allows the prediction of the protective action of filters and respiratory protection in general.

Thermal action of pulse radiation on the carbon conic shells loaded with internal pressure

The new mechanism of constructions destruction as a result of thermal action of radiations and particles fluxes was considered. It is supposed that interruption of construction operability comes owing to non-stationary processes of deformation and destruction. Non-stationary deformation and destruction take place as a result of action of quasi-stationary working loadings at saltatory change of construction rigidity. Jump of rigidity arises at volume and impact heating of material by means of action of radiations and particles fluxes.A numerical method for predicting of the thermal and tension-strain states of thin-walled orthotropic constructions having variable thickness under the action of energy fluxes of different physical nature are considered. Physical and chemical processes in result of heating of composite construction materials were taken into account. These processes are the binder pyrolysis, chemical reactions of carbon and air flow components, and the ablation of carbon residue. Non-stationary processes occurring in the shell has been numerically simulated. Model of layer-by-layer destruction is used in this simulation.

Study on Ignition Delay Time of Al/Mg Fuel-rich Propellant under Tangential Air Flow

Solid propellant, as the power source of propulsion system, has obvious influence on the internal ballistic characteristics of ramjet. The ignition and combustion charac-teristics of solid propellant help to reveal the combustion mechanism and have im-portant guiding significance for estimating the performance of propulsion system. In this paper, the ignition and combustion characteristics of Al/Mg fuel-rich propellant under tangential air flow were studied. Laser ignition experiment was carried out on the Al/Mg fuel-rich propellant at different tangential air flow rates and tangential air flow components. The results show that the air flow rate and air flow composition can affect the flame shape and the brightness of the propellant. At the same time, with the increase of air flow rate, the more obvious the erosion combustion effect on the pro-pellant burning surface. The air flow rate also affects the ignition delay time. When the air flow rate is low, the ignition delay time decreases with the increase of air flow rate. When air flow rate is 0.8L/min, the ignition delay time is reduced to the mini-mum of 350ms, but with the air flow rate continues to increase, the ignition delay time is increasing. As the oxygen content in the air flow increases, the ignition delay time increases. However, when the oxygen content is less than 14% or higher than 21%, the effect of oxygen content on the ignition delay time is weakened.

Objective and quantitative evaluation of intellectual productivity under control of room airflow

In order to design a work environment that improves office workers’ intellectual productivity, the authors have focused on airflow, which is a key factor in thermal environments. An airflow control method that improves the degree of concentration is proposed, and its effectiveness is evaluated objectively and quantitatively by evaluative experiments. The designed airflow environment is composed of two airflow components: a stimulative airflow and a mild airflow. In this experiment, cognitive tasks are given to participants. The concentration time ratio (CTR), which is a quantitative and objective evaluation index of the degree of concentration, is measured. The results show that the average CTR under the proposed airflow condition is 61.1%, while that under the no airflow condition is 54.6%. The proposed airflow control shows a significant improvement in CTR, with an increase of 6.5% (p < 0.001). Consequently, our findings suggest that intellectual work can be performed better in an environment that fosters a high concentration time ratio.

Atmospheric forcing of upwelling along the south-eastern Baltic coast

The meteorological forcing on the occurrence of upwelling along the south-eastern Baltic Sea coast (Lithuanian-Latvian sector) is analysed in this study. The sea level pressure patterns and the locations of pressure centres inducing and inhibiting upwelling were identified. The research was performed for the years 1982–2017, for the months of May–September, when the sea waters are thermally stratified and the phenomenon is detectable. The frequency of upwelling is the highest in June (approximately 15%), July and August (11–13%) and the lowest in September (7%). The central and northern part of the Lithuanian–Latvian coast is most favourable for upwelling occurrence (frequency up to 20% in summer months). The main features of the sea level pressure patterns that induce upwelling in the research area are positive pressure anomalies spreading over Northern Europe and the Norwegian Sea, while negative anomalies encompass Southern Europe. Airflow around the anticyclonic centres gives a north-eastern component to the wind direction over the Lithuanian-Latvian shore. Two circulation types were recognized as inducing the occurrence of upwelling along the Lithuanian–Latvian coast. Both of them are characterized by the anticyclonic centres located west or northwest of the study area and intensify the northerly or north-easterly airflow over the research area. Different pressure patterns with the negative anomalies of sea level pressure spreading over the North Sea and the positive anomalies underlying Central Europe inhibit upwelling along the Lithuanian–Latvian coast. Such pressure conditions, bring about the western airflow component. More constant western winds restrain the upwelling process and bring about normal thermal stratification of coastal waters. A detailed analysis allowed the recognition of two circulation types inhibiting coastal upwelling in the study area. They reveal dipole patterns of sea level pressure anomalies, but the two inhibiting patterns differ substantially in the intensities and locations of the pressure centres and in wind conditions.

Heartbeat Signal Detection From Analysis of Airflow in Rat Airway Under Different Depths of Anaesthesia Conditions

We inserted a tubular flow sensor incorporating micro-electro-mechanical systems technologies directly into the rat airway and analyzed the airflow waveforms obtained under different depths of anaesthesia conditions by using discrete Fourier transformation (DFT) to evaluate the heartbeat frequency. The electrocardiogram (ECG) signal was used as the reference heartbeat frequency. The calibration curve of the flow sensor used to measure the oscillating airflow in the rat airway was determined on the basis of King’s law. The airflow waveform at the rat airway caused by only the heartbeat was measured by applying deep anaesthesia; the waveform frequency coincided with the simultaneously measured ECG signal frequency. DFT analysis of the airflow signals measured under deep and shallow anaesthesia conditions verified the fundamental heartbeat frequency values. The airflow components related to heartbeat motion were successfully extracted by using the heartbeat frequency spectrum. The respiration and heartbeat signals were thus successfully detected.

A Bayesian neural network approach to compare the spectral information from nasal pressure and thermistor airflow in the automatic sleep apnea severity estimation.

In the sleep apnea-hypopnea syndrome (SAHS) context, airflow signal plays a key role for the simplification of the diagnostic process. It is measured during the standard diagnostic test by the acquisition of two simultaneous sensors: a nasal prong pressure (NPP) and a thermistor (TH). The current study focuses on the comparison of their spectral content to help in the automatic SAHS-severity estimation. The spectral analysis of 315 NPP and corresponding TH recordings is firstly proposed to characterize the conventional band of interest for SAHS (0.025-0.050 Hz.). A magnitude squared coherence analysis is also conducted to quantify possible differences in the frequency components of airflow from both sensors. Then, a feature selection stage is implemented to assess the relevance and redundancy of the information extracted from the spectrum of NPP and TH airflow. Finally, a multiclass Bayesian multi-layer perceptron (BY-MLP) was used to perform an automatic estimation of SAHS severity (no-SAHS, mild, moderate, and severe), by the use of the selected spectral features from: airflow NPP alone, airflow TH alone, and both sensors jointly. The highest diagnostic performance was reached by BY-MLP only trained with NPP spectral features, reaching Cohen's κ = 0.498 in the overall four-class classification task. It also achieved 91.3%, 84.9%, and 83.3% of accuracy in the binary evaluation of the 3 apnea-hypopnea index cut-offs (5, 15, and 30 events/hour) that define the four SAHS degrees. Our results suggest that TH sensor might be not necessary for SAHS severity estimation if an automatic comprehensive characterization approach is adopted to simplify the diagnostic process.

Effects of ambient conditions on multi-capillary ventilation rate

As a major physical parameter for the tobacco industry, the ventilation rate of cigarette should be measured reliably. Theoretical and numerical investigation on ef-fects of ambient conditions (e. g., cumulative flux of ozone and additional pressure drop) on the ventilation rate was carried out. It was found that the standards exhibited a non-linear airflow component, which explains why additional pressure drop has an effect on the calibrated value, and had low sensitivity to cumulative flux of ozone.

Numerical simulation of aerodynamic suspension of particles during wind erosion

The wind erosion is the main cause of many environmental phenomena such as desertification, dust haze, sandstorms, and energy balance changes in the atmosphere. Wind erosion occurs when the friction velocity exceeds the threshold friction velocity. Threshold friction velocity depends on many parameters such as surface roughness, heat flux, moisture of soil and soil texture. In this article, the horizontal and vertical fluxes of particles due to wind erosion have been studied using a numerical method. Atmospheric boundary layer has been modeled with computational fluid dynamic for different wind profiles and the flow field near the surface has been solved. The values of velocity’s components of air flow have been used to calculate wind erosion fluxes according to balance equations of particles. The erosion flux of particles in terms of suspension, saltation and creeping have been calculated according to threshold friction velocities. Finally, the relation between fluxes has been determined and the correlation of erosion flux and direct suspension in terms of friction velocity and particle diameter has been presented. Comparing the results with previous works revealed that the value of direct suspension of particle C (kg/ms) is related to total erosion flux Q (kg/ms) as Q = 30,553 C2 + 6.4316 C + 0.0017.

Consecutive transcranial magnetic stimulation twitches reduce flow limitation during sleep in apnoeic patients

What is the central question of this study? A transcranial magnetic stimulation (TMS)-induced twitch applied on isolated single breaths over the motor cortex somatotopic representation of the tongue briefly recruits submental muscles and improves airflow dynamics of flow-limited respiratory cycles without arousing sleep apnoea patients. However, the mechanical impact of the TMS-induced twitch applied during consecutive breathing cycles on airflow dynamics remains unknown. What is the main finding and what is its importance? Our results show that application of TMS with the stimulator output set at the sleep submental motor threshold intensity on consecutive respiratory cycles increases inspiratory flow and reduces the turbulent airflow component. These results indicate an improvement of airflow pattern after two single consecutive TMS-induced twitches without arousing sleep apnoea patients. Transcranial magnetic stimulation (TMS)-induced twitches applied on isolated breaths briefly recruit upper airway dilator muscles and improve airflow and inspiratory volume without arousing apnoeic patients from sleep, but the effects of applying such twitches consecutively on airflow dynamics is unknown. The objective of this study was to quantify the effects of five consecutive TMS-induced twitches applied on sleep-induced obstructive hypopnoeic breaths in 10 obstructive sleep apnoea patients. Submental muscle motor threshold (SUBMT) and motor-evoked potential were measured during wakefulness and sleep. The TMS-induced twitches were applied during stable non-rapid eye movement (NREM) sleep, at the beginning of inspiration of consecutive flow-limited respiratory cycles, with the stimulator output set at sleep SUBMT. Maximal inspiratory flow, inspiratory volume, inspiratory time, shifts of electroencephalogram frequency and pulse rate variability were assessed. During sleep, SUBMT increased (wakefulness, 25.3 ± 4.9%; NREM sleep, 27.0 ± 6.2%; P = 0.02). During each series of stimulations there was a rise in maximal inspiratory flow (from 306.7 ± 123.2 to 359.8 ± 154.1 ml s(-1); P = 0.0002) and in inspiratory volume (from 346.1 ± 128.1 to 414.9 ± 171.2 ml; P = 0.02) without differences in thoraco-abdominal efforts and inspiratory time. These responses were observed in the absence of arousals and ceased immediately after TMS interruption. Transcranial magnetic stimulation-induced cortical and/or autonomic arousal was observed in 30.2% of all series of stimulation. Consecutive twitch TMS of submental muscles may lead to arousals in a minority of patients but can be applied on consecutive respiratory cycles during sleep and can significantly improve maximal inspiratory flow and inspiratory volume of flow-limited cycles.

Study on a Change in the Behavior of Flame on Bluff-Body under the Transitional Regime by Swirled Air Flow

The experimental study to investigate the effect of the swirling annular airflow by swirler with guided vanes for flame behavior under the transitional regime on a double concentric bluff-body burner was conducted. Propane gas was employed as the fuel gas and the swirler of the five types was prepared. The result shows that the swirling component of airflow makes a grate contribution to improve the flame stability and suggests that the geometrical swirl number larger than 0.6 and airflow velocity which exceeds a certain value are need to improve the stability. However, the result of the visualization of the flames reveals that the spread airflow by centrifugal force, which is prevented from mixing with fuel, accompanies stabilized flame. The result gives a surmise that it is difficult for the present burner to combine the flame stability and the perfect combustion.

A model for integrating passive and low energy airflow components into low rise buildings

Integrating passive systems such as cross and stack ventilation, a solar chimney, a wind tower or an earth-air tunnel into a building envelope has the potential to significantly reduce the ventilation and air-conditioning demand on buildings. However the application of combination of these features in low rise contemporary buildings is limited. Among the major reasons, is the lack of simple building modelling techniques preventing effective integrated passive systems. Existing coupled multi-zone airflow and thermal modelling software such as COMIS-TRNSYS, CONTAM-TRNSYS or TRNFLOW do not include the passive airflow components which require simultaneous prediction of temperature and airflow rate in the components such as solar chimneys and wind-induced earth-air tunnels. This paper develops an integrated model incorporating these passive airflow components into a coupled multi-zone ventilation and building thermal model. The model is validated against COMIS-TRNSYS software for a lightweight building with large openings. The prediction of each passive airflow component is validated with available published analytical and experimental findings. The solar chimney model is able to predict reverse flow and accurately predicts the air temperature in the chimney. The earth air tunnel (EAT) considers the transient heating up effect of the soil during operation and predicts the outlet air temperature.

Aero‐Acoustic Optimisation of Airflow Components in Gas Turbines

AbstractThere is always a great interest in the improvement of the efficiency of gas turbines. This requires the reduction of energetic losses like pressure losses induced by vortices, turbulence and secondary flow. In the current investigation, effects caused by aero‐acoustic oscillation are of interest. The possibility to control these effects or to make them usable has several advantages, for example reducing pressure losses, reducing noise, and influencing the heat transfer and charging effects. This concerns potentially oscillatory flow systems in gas turbines like pipes, cavities and annuli. In particular annuli can not be considered theoretically using one‐dimensional pipe acoustic. The start of oscillation occurs due to turbulent shear stress, solid oscillating surfaces and time fluctuating pressure fields as well as thermal stimulation. This study focuses on the impact of aero‐acoustic oscillation caused by shear stress and rotating pressure fields on the through flow. A numerical study of axial, radial and circumferential acoustic eigen‐modes and a time harmonic analysis have been done with several boundary conditions. The achieved results have to be proved in a further experiment. An improvement in the aero‐acoustical design of gas turbine flow components will be possible thanks to the results gained from both the numerical study and planned experiment. (© 2009 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Perfiles de Velocidad en el Cilindro de un Motor Alternativo

The present work objective is to show experimental results for speed components of air flow admitted in a CFR engine simulated cylinder (Cooperative Fuels Research), installed in a stationary flow bench provided with a data acquisition system. The speed components were measured using a calibrated hot wire anemometer. Measurements were made for different admission valve lifts on different points on several cylinder cross-sectional planes. As a result, the speed profiles on the planes considered in the study were obtained. From these profiles the presence of swirl and tumble in the interior of the engine cylinder was verified.

System for measuring velar function during speech

A method of and device for the diagnosis and treatment of speech dynamically measures the functioning of the velum in the control of nasality during speech. Various components of oral and nasal airflow are separated and selectively analyzed including (i) the fundamental frequency component of each airflow during voiced speech, (ii) a plurality of voice components that cover a frequency range encompassing at least the lowest vocal tract resonance (the first formant), and (iii) the subsonic and infrasonic components of at least the nasal airflow. By comparing the nasal and oral airflow components at the voice fundamental frequency, a nasalization measure for voiced speech sounds is formed which emulates methods that compare low frequency nasal and oral airflow during voiced speech, while eliminating or greatly reducing the problems associated with comparing these low frequency airflows, and which improves upon previous methods based on measuring and comparing nasal and oral radiated sound pressure. A circumferentially vented screen mask (C-V mask) is configured with separate nasal and oral chambers to separate the two airflows, and causes only a minimal distortion and muffling of the voice. The separate nasal and oral airflows are detected and filtered, and a ratio of the two is formed to provide a visual display used to detect and correct abnormal or incorrect speech formation and word pronunciation.

A wind tunnel study of organised and turbulent air motions in urban street canyons

High concentrations of car-exhaust gases in urban street canyons are typically associated with low wind velocities or situations when the wind blows perpendicular to the canyon axis. The latter flow configuration has been studied in a wind tunnel model of a street canyon. The mean flow and turbulence structure have both been investigated and comparisons have been carried out with results of full-scale flow measurements in urban street canyons. A qualitative similarity has been found between the results of atmospheric measurements and flow characteristics in the modelled street canyon. Data from all employed sources give evidence of a flow acceleration (in some cases, rather sharp) above roof level. Additionally, the effects of traffic on the organised and turbulent components of airflow in the canyon have been quantified. The experimental data show significant differences in flow and turbulence patterns corresponding to the model cases of one-way and two-way traffic.

Pneumotachograph mask or mouthpiece coupling element for airflow measurement during speech or singing

A pneumotachograph mask or mouthpiece coupling element may reduce the distortion and muffling of the voice otherwise caused by a mask or mouthpiece when measuring the low-frequency components of a volume-velocity of oral or nasal airflow during speech or singing. This improved performance is accomplished by separating the low-frequency components to be measured from the higher frequency or acoustic components by an acoustic filter. The filter passes much of the acoustic energy through the walls of the mask or mouthpiece at a location or locations close to the face. The lower frequency airflow components are funneled by the mask or mouthpiece coupling element through an airflow-measurement transducer. The acoustic filtering can be implemented by a membrane, or array of membranes, in the wall of a chamber located close to, or formed as part of, the mask or mouthpiece. An optional inertive-impedance-forming constriction may be placed in the flow pathway between the chamber and the airflow transducer to provide additional acoustic filtering. By making the acoustic filtering process sufficiently thorough, the low-frequency components funneled by the mask or mouthpiece to the transducer contain none of the momentary reversals in flow direction that normally occur during egressive voice production. The mask or mouthpiece coupling element may be used with a transducer that only measures unidirectional flow. Additional acoustic filter elements may be added in the flow path to the transducer and may further reduce the acoustic energy reaching the transducer.